Concave mirror is used in headlights of vehicles, because it
- A.focuses light from the bulb onto nearby vehicles
- B.sends parallel rays
- C.fits well into the shape of the headlight
- D.is cheaper than other mirrors
Correct answer
Explanation
The correct answer is B, sends parallel rays. The bulb of a headlight is placed at the principal focus of a concave mirror, so the reflected light leaves as a strong beam of parallel rays that reaches far down the road.
A concave mirror reflects rays coming from its focus parallel to its principal axis. Because the parallel beam does not spread out, its intensity stays high over a long distance, which is exactly what a driver needs at night. The same property is used in torches and searchlights. Working the other way, a concave mirror gathers parallel rays to its focus, which is why it is used in solar cookers and in shaving and dentists' mirrors, where it gives an enlarged image of a nearby face or tooth.
A is wrong: the aim is to light the road ahead, not to focus light onto nearby vehicles. C is wrong: the shape of the headlight follows the mirror, not the other way round. D is wrong: cost is not the reason; the parallel beam is.
Exam tip: headlights, torches and searchlights use concave mirrors with the bulb at the focus; rear-view mirrors are convex.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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